1. Field of the Invention
The present invention relates to a small-sized tiller and, more particularly, to a small-sized tiller which can easily be steered even when its tilling claw runs onto hard ground or a solid object such as a stone buried in ground during tilling work.
2. Description of the Related Art
In recent years, small-sized tillers designed to be smaller than tillers for exclusive use in farms have been widely used as tillers for kitchen gardens or small fields, because such small-sized tillers are easy to handle and have small turning circles. Japanese Utility Model Laid-Open Publication No. SHO-57-86502, for example, discloses a small-sized tiller which runs while tilling soil by the rotation of a tilling claw fitted to a tilling shaft.
The small-sized tiller has a transmission fitted to the lower portion of an engine, a rotating shaft fitted to the lower portion of the transmission, and plural tilling claws fitted to the rotating shaft in such a manner as to be spaced apart from one another at predetermined intervals. The small-sized tiller runs while effecting tilling by means of the plural claws. This small-sized tiller has a manipulating handle fitted to the rear upper portion of the transmission. A resistance bar is fitted to the transmission, and extends downwardly from the rear of the transmission. The resistance bar is inserted into ground during tilling work.
If the tilling claws strike on a hard solid object such as a stone during tilling work using the small-sized tiller, the tilling claws ride onto the solid object and the tilling shaft bounds upwardly, causing a phenomenon which causes the small-sized tiller to bound owing to a tilling reaction force. Shock energy at this time conducts from the tilling claws to the transmission, the engine and the manipulating handle via the rotating shaft. In particular, if the right or left tilling claws as viewed from an operator strike on the solid object, the tiller will bound on its right or left side and will lose the balance between the right and left sides.
If the operator is to steer the small-sized tiller subjected to shock energy while keeping the balance between the right and the left sides, or is to restrain the bounding phenomenon, (1) the operator needs to adjust the length by which to insert the resistance bar into ground, by appropriately setting the height at which to fit the resistance bar, according to the conditions of soil, or (2) the operator needs to adjust the load under which to insert the resistance into ground, by applying an adequate downward manipulating force to the manipulating handle during tilling work. In this way, it is possible to adjust the resistance force of the resistance bar against the shock energy.
However, even if the operator can adjust the length by which to insert the resistance bar into ground and the load under which to insert the resistance into ground, the operator will need experience and intuition to steer the small-sized tiller subjected to the shock energy while keeping the balance between the right and left sides thereof, or to restrain the bounding phenomenon.
Furthermore, a large number of cultivated lands such as fields have surfaces with uneven areas among ridges, and differ in the hardness of surface soil. If such ground is tilled with the small-sized tiller, the amount of tilling by the left tilling claws will differ from the amount of tilling by the right tilling claws. In this case, how to maintain the rectilinear running of the small-sized tiller while keeping the balance between the right and left sides of the same has influence on the degree of finish of tilling. For this reason, the operator needs experience and intuition to adjust the length by which to insert the resistance bar into ground and the load under which to insert the resistance into ground, and steer the small-sized tiller while keeping the balance between the right and left sides of the same.
Accordingly, since the operator needs skill if the operator is to steer the related art small-sized tiller for tilling work, there has been a demand for an improvement in the small-sized tiller.
The present invention has been made in view of the above-described points, and aims to provide a small-sized tiller which is at all times easy to steer and enables far easier tilling work.
According to an aspect of the present invention, there is provided a small-sized tiller characterized by a power source, a power transmission mechanism for transmitting a rotational driving force of the power source to a tilling shaft, plural tilling claws fitted to the tilling shaft and arranged to cause the tiller to run, by rotating while tilling ground, a resistance bar to be inserted in ground, and a manipulating handle which is swingably fitted via a pivot to a rear portion of the power source or a rear portion of the power transmission mechanism.
The manipulating handle is upwardly and downwardly swingably fitted to the rear portion of the power source or the rear portion of the power transmission mechanism.
A damping member for effecting damping when the power source and the power transmission mechanism swing upwardly or downwardly with respect to the manipulating handle is interposed between the power source or the power transmission mechanism and the manipulating handle.
A first link is upwardly and downwardly swingably fitted to the rear portion of the power source or the rear portion of the power transmission mechanism, while a second link is forwardly and rearwardly swingably fitted to the manipulating handle, the first link being connected to the second link to constitute a link mechanism which can be bent according to a forward or rearward swing of the power source and the power transmission mechanism. One end of a damping member is forwardly and rearwardly swingably connected to a connection portion between the first and second links, while the other end of the damping member is forwardly and rearwardly swingably connected to the manipulating handle, to enable the proportion of the stroke of the damping member per predetermined amount of swing to vary to a larger extent as the power source and the power transmission mechanism swing in a direction in which the power source and the power transmission mechanism approach the manipulating handle.
The resistance bar may be fitted to extend downwardly from the manipulating handle or to extend downwardly from the rear portion of the power transmission mechanism.
During tilling work with the tiller according to the present invention, if the tilling claws strike on a solid object such as a stone buried in ground, a bounding phenomenon occurs due to a tilling reaction force. Shock energy which is the tilling reaction force at this time conducts from the tilling claws to the power source and the power transmission mechanism. Since the resistance bar is inserted in ground, the resistance bar has a resistance force against the bounding phenomenon, whereby the resistance bar and the manipulating handle are in a stable state. Since the tilling claws, the power source and the power transmission mechanism swing, particularly upwardly, with respect to the manipulating handle which is in such a stable state, the shock energy can be absorbed. The manipulating handle is stable without bounding, and the steering of the tiller becomes easy.
It is preferable that the damping member for effecting damping when the power source and the power transmission mechanism swing upwardly or downwardly with respect to the manipulating handle be interposed between the power source or the power transmission mechanism and the manipulating handle, because when the power source and the power transmission mechanism swing upwardly or downwardly with respect to the manipulating handle, shock energy can be fully absorbed by the damping member.
A suspension made of the link mechanism and the damping member is a progressive suspension in which the proportion of the stroke of the damping member per predetermined amount of swing varies to a larger extent as the power source and the power transmission mechanism swing in the direction in which they approach the manipulating handle. The damping member absorbs a smaller shock energy with a smaller stroke and a larger shock energy with a larger stroke. Accordingly, the damping member can effectively absorb shock energy.
Since the resistance bar extends downwardly from the manipulating handle, during tilling work, the length by which to insert the resistance bar into ground can be adjusted to stabilize a tilling depth, by applying an adequate downward manipulating force to the manipulating handle. Moreover, it is preferable that the resistance bar be extended downwardly from the rear of the power transmission mechanism as described above, because when a bounding phenomenon occurs, the resistance bar is inserted into ground to restrain the swing of the power source and the power transmission mechanism.
Moreover, in the present invention, the manipulating handle is fitted via a pivot to the rear of the power source or the rear of the power transmission mechanism so that the portion forward of the pivot can swing rightwardly and leftwardly with respect to the manipulating handle as viewed from the operator, thereby absorbing shock energy. In particular, even if the amounts of tilling by the right and left tilling claws differ from each other and the right and left tilling reaction forces differ from each other, the tilling claws, the power source and the power transmission mechanism rotate about the pivot and incline rightwardly or leftwardly with respect to the manipulating handle, thereby absorbing the right and left different tilling reaction forces. Accordingly, the manipulating handle is stable without bounding or inclining, and the operator can steer the small-sized tiller while keeping the balance between the right and left sides of the small-sized tiller.
A pair of right and left damping members for reducing shock occurring due to the rightward and leftward swing of the portion forward of the pivot are interposed between the power source or the power transmission mechanism and the manipulating handle, whereby shock energy is absorbed by the damping members.
A pair of right and left arms are respectively extended from the manipulating handle toward the right and left sides of the power source or the right and left sides of the power transmission mechanism, and the right and left sides of the power source or the right and left sides of the power transmission mechanism are respectively connected to the ends of the pair of right and left arms by a pair of right and left links, the pair of right and left damping members being interposed between the pair of right and left links and the manipulating handle to convert a rightward and leftward swinging motion of the power source and the power transmission mechanism into a forward and rearward swinging motion through the pair of right and left links and transmit the forward and rearward swinging motion to the pair of right and left damping members. Accordingly, in the above-described construction, it is possible to freely set the strokes and arrangement of the damping members, as compared with a case in which the right and left swinging motion of the power source and the power transmission mechanism is directly transmitted to the right and left damping members. In particular, the damping members can be disposed so that they can be expanded and compressed toward the front and the rear of the vehicle body of the small-sized tiller, whereby the small-sized tiller can be made far more compact.
It is preferable that the resistance bar be extended downwardly from the manipulating handle, because the length by which to insert the resistance bar into ground can be adjusted to stabilize the tilling depth during tilling work, by applying an adequate downward manipulating force to the manipulating handle.